Production of prestressed building elements



May 15, 1956 M. R. RO

PRODUCTION OF PRESTRESSED BUILDING ELEMENTS Filed Aug. :0, 1952 2 Sheets-Sheet 1 Inns-#7224 May 15, 1956 E; 2,745,164

PRODUCTION OF PRESTRESSED BUILDING ELEMENTS Filed Aug. 30, 1952 2 Sheets-Sheet 2 United States Patent PRODUCTION OF PRESTRESSED BUILDING ELEMENTS.

At present it is customary to produce'pre-stressed concrete on long tracks above which steel wires are stretched. The concrete surrounding the wires is charged into shuttering, "and after sufiicient setting of the concrete the wires are released and cut. Instead of shuttering to be filled with concrete a line of moulded bricks provided with grooves for the reception of the reinforcing wires may be used, said grooves being filled'with mortar.

The necessity of having to apply concrete and shuttering and moulded bricks respectively to the production track along the whole of its considerable length and'to compact the concrete by vibration leads to tedious transport and complicated manufacturing operations.

Therefore the suggestion has been made to arrange a table at a certain point of the production track where the shuttering is assembled and the concrete is charged and compacted. The elements thus produced are then pushed along the reinforcing Wires to their positions on the production tables where a second vibration takes care of a renewed tight envelopment of the Wires by the concrete. After setting the elements are drawn by the wires to a further table where the shutteringfis removed and the wires are out between the individual 'elements. In this manner a certain rationalization can be achieved. The following disadvantages, however, still exist: For one it is necessary to lay out and pre-stress the wires on each track again after completing the production of a certain number of building elements; furthermore the elements contained in their shuttering have to be slid along the wires, necessitating as a rule that at the final setting place the concrete has to be compacted once more by vibration.

. The aim of the present invention isto eliminate the described disadvantages. The invention relates to a method for producing pre-stressed building elements as well as to a device for carrying out said method;

The method according to the invention, is characteriz'ed in that a reinforcem ent of any desired length is mowed 'across'a progressive production support and is simultaneously brought to the desired initial tension, and that the building elements are formed on the progressive production'support by embedding the reinforcement in concrete,.wh'ereupon they are fed through a setting duct and thereafter are cut apart, care being taken that the initial tension in the reinforcement stretched along the,

progressive production support is maintained at all times. The device for carrying out said method is characterized by a progressive production support for the elements to be produced provided with means for. advancing the building elements, at least one stock'spool forat least one reinforcing wire stretched longitudinally across the progressive production support in connection with a wire tensioning device arranged in advance of said support, andin addition by a setting duct through which said progressiveproduction support passes, and a cutting-01f or for dividing the-individual building elements.

severing" device arranged towards theend of said support 2,745,164 Patented May 15, 1956 By way'of example several embodiments of the device according to the invention are shownin the drawings accompanying and forming part of this Specification in which: i Y

Fig. 1 is a first form of construction of the device shown diagrammatically in side elevation;

Fig. 2 is a second form of construction of'the device, likewise in side elevation;

Fig. 3 is a third example of construction of the device in top view;

Fig. MS a fourth example of construction-of the device in top view; and t Fig. 5 is a fifth form of construction of the-device top view.

According to the form of construction shown in'Fig. 1

the device has a progressive production: belt 1 passing the guide pulley 6b the reinforcement 4 passes longit'ue dinally above the conveyor track 1 and is anchored a endlessly over the rollers 2a, 2b, the rollers 2a being the driving rollers. It is assumed that the endlessly designed production'belt 1 moves in the direction of the arrow P. Adjacent to the driving roller Zaof the production belt there is located a production table 3., p

The reinforcement consistingof at least one reinforcing wire 4 is led from a stock" spool 5 arranged in front of the production belt over the guide pulleys 6a, 6b and the pulley 7 from which a weight'8 is suspended, From releasable lock 9 by which the wound-on reinforcing wire 4 is prevented from unwinding from the stock spool 5. Instead of the weight an hydraulic press might'be provided for tensioning the reinforcement The ;hy-

draulic press 30, seen in Fig. 5, comprises a'pis'ton moving in a cylinder. The hydraulic fluid prevents the, rotation of the stock spool, as illustrated. I

On the production table 3 the pre-stressed reinforcing wires already provided in the right number and distribution are surrounded by molding means such as an' en closure or way of example by a shuttering, and the latter is filled with binding material. The building elements to. be produced are already given theirshape on theproduc tion table 3 so that with exception of the setting and,,.the removal of the shuttering the production procedure'is completed at this point. i I

The production belt 1 which is provided with special drivers 10 pushes the element 11 lying on the production table 3 into the heating duct 12; Forfthis purpose the drivers 10 may abut against the shuttering to'which the wires 4 are connected, or they may be connected directly to the wires 4. The shuttering may be connected'frictionally to the wires 4 whereby the clamping action of the component parts of, the shuttering will be suificientopull the shutterings along with the wires.

After passing the heating duct 12 the element 11 has been artificially set so that the set elements. 11 issuing from the heating duct 12 can have the shuttering removed. On its return to the driving roller 2a the production belt 1 can carry along with it the shuttering elements inasfar as such arerequired for the production of the elements.

In the rear of the heating duct 12, but still above the production belt 1, there is provided a cutting device 13 by which the reinforcing wires 4 are cut apart between the individual elements 11 so that the finished elements can be fed onto a roller table 14 arranged behindthe production belt for their removal. i I The anchoring of the fire-stressed wire 4 takes place, in the foremost set element 11 which issup ported o' n' the production belt 1 by means of the driver 10a. As

WeightiS is lifted. By releasing the locking-device 9 atthe stock; spool the'v weight 8: can again be; lowered.

Stock spool 5 comprises a toothed wheel, which uponrotation feeds;- wire: 4; Locking device 9'comprises a toothed rack which; can efiecttthe requisite-rotation of stoclc.spool:5'; By. locking'sthe toothedrack against move ment, the stock spool is also prevented'from moving and the; desired tension: can. be; maintained;

At the start of production there is not thezpossibility of:.anchoring -.the:reinforcement in: the set:.elements .as at that moment no such elements are yet in-existence'. In: this 1 case: the. procedure 115.135. follows The weight 8 is first of all locked by preventingrelativermovernent ofzspoolfi. and toothed rack. 9. Then the reinforcing wires14-are secured to the :driversll) by means ofr'a special.device. andiare'then put under; initial tension. by. operation. of. the. drive 2a,v whereupon production of; theelementsscanstart. As soonas the first element with thegspecial. securing device. reachestthe cuttingmachine 13, said device cantberemoved from the driver, since the anchorage .of.the.reinforcement1is ensuredby the elements set .in the heating,duct.-12 themselves.- The special device. may compri'sea notch-in drivers.10. which notch. is lined withfrictional..material, thereby assuring seating. of .the'

wires .4 in. the.notch .and simultaneously preventing; relatiye rntfwen entof. the wires and. drivers. Alternately, a. spring; clamp. may be seated. in the apex of thexnotch to securethewires .4in position.

' The operators. have toattend to:

' (1.).Tlie-..production table 3 where the main work is. carried. out, namely shuttering, charging of the material, vibratingandfromwhere the feed of. the production beltv 1" is: controlled;

(2), The cuttingmachine 13, and

(3) The roller. table 14, where; the. finished elements.

are loaded for. conveying to store.

The advancing speed offtheproduction belt 1 and thusthe output of the device. is conditioned by:

(1)) The time required for producing one element on the production table,

(2) The settingtitne. in the heating duct.

By the correct choice. of the length of the heating duct an advancing speed can be used which depends onthe production time at the production table only. If the. length 'of' tlie heating duct is not to be too great, several elements might be produced'side by side. on theproduction table.3 by oneworker, said elements also moving on side. by. sideon one and the same production belt.

Theadvanceof the production belt 1 can at will takev place continuously or intermittently.

Theaemploymentofa weight 8 is not necessary for obtaining theinitialtension of the reinforcement. The initial. tension'tcanwalso' be obtained bya. co-action of the: drivezflmand the.lock.9 adapted to'each other. Furthermore, instead of: having the'production belt with the drivers take: up the pre-stress force andall frictional forces; an arrangement could be'provided with which' the production beltand thedrivers would have to overcome tlie'frictionalforces only, whilst a special feed' dee vice"'located"atthe outgoing end would take up the prestress'"force'. I'n'themost simple case there is a sliding plane insteadv of the. production belt. In this casethe. feed. device handles the sum of the pre-stress forces and the frictionaliforces.

' The. example. of embodiment shownin Fig. 2 employs a'stationary table 3, 3a instead of a conveyor belt, said stationary table serving as a production support of the b'ui1ding .elements. to be produced. For reducing. thefi'iction-duringfeeding of the elements the; production table can be provided with special means such as closely spaced rollers. formingv the.v support. for. the..elements..

This embodiment is particularly suitable for the production of the building elements by means of shutterings 15. Each shuttering is connected at its rear side to the reinforcement 4, for example by clamping plates clampable to the reinforcement; as is" indicated in the drawing at 16. For. the feed of the elements and the shutterings 15 respectively and for the: initial. tensioning-ofthe-reinforcement a driving roller 17 is arranged at the end of the progressive production table. to which, by way of example by the interposition of a pulley block, a reciprocating draw belt 18"issecured the free ends of which can be linkedi to. the shuttering ofan element already, setor to the reinforcement directly by means of a hook or the like for the purpose of advancingthe elements. Before being led over the progressive production table, the reinforcement unwound from the stock spool 5 is passed through a-tensioning device consistingxof za roller. 19 provided with a catch or toothed rack, the arrangement:

being such that the catchof. the roller'19 is-madesto co-operate with. the driving roller. 17 in. such a manner;

that the reinforcement is always maintained at the prevscribed tension, even during feeding'thereof. To achieve this the driving roller 17 is at all times rotated slightly;-

more than the roller 19 thus tobalance the linear exten: sion of.the reinforcement resulting from the initial. tensioning.

ASfS0OI11aS th6 draw belt 18 has advanced a coupled buildingelement by its forward movement towards v the driving roller-.117. and thus all the. elements on the. pro.

duction: support. connected to the reinforcement 4-have advancedby one step from a.-a to bb a. securing member. 20- of beam-like shape and abutting. against special; abutments is placed behind the next-following element 15 at aa in order to maintain the initial tension. inithe reinforcement 4, whilst the draw belt 18 is released;

and its end provided with the hook is returned, for

exampleby hand, from bbto a-aand ishooked to.

the next element. The cutting-01f device 13 for separating the; individual elements can come into operation whilst the securing member 20 is in engagement. The two rollers 17 and 19 may with advantage be electric winches.

Obviously the two examples of construction may be combined, e. g. in such a manner that in. they device.

according to Fig. 2 the progressive-production support.

is anv endless conveyor belt which may or may not be provided withdrivers and is in connection with a drive themovements of which being additionally coordinated.

method. Once. the reinforcements have been anchored.

any desired lengths can be produced without interruption since, after. exhaustion of the supply on the spools the. reinforcingwires can be lengthened by joining. Thus with the most rationalized, normal'method of. operationby increasing the working time or by introducingshifb work there-is the possibility hitherto unattainable with pre-stressed concrete of increasing the production output without having to expand the existing plant. special arrangement according to the invention allthe well-known advantages of progressing production are. exploited; Compared with the so-called' tension table method considerable. saving of working time results by avoiding pauses, by simplifying the operating cycle, by reducing the various types of operations and by extensive mechanization.

To. permit more or lessheavily reinforced building; elements. to. be produced on the same production line. without interruption it must bev possible to changp. the" By the number of reinfor'cing'wires at any time without atfecting the initial tension of the reinforcing wires inthe element in the process of production at the time. This is'possible with the constructions of the device according to Figs. 3 to 5, which represent top views of devices generally similar to that of Fig. 2. The several reinforcing wires 4a and 4b are equivalent to .wire 4 ;of'Fig.; 2.

The wires are fed from respective sources while maintained under uniform stress. They are separated into an inner group and an outer group and these groups are displaced relative to each other between two positions. In displacement towards each other, the number of reinforcing wires in each element is increased. In displacement away from each other, the number of reinforcing wires is decreased. This is effected by the use of coupling means to which all of said wires are connected. Winches may be employed to maintain the stress on the wires being displaced, the winches being positioned on that side of the coupling means where the groups of wires are more distant from each other.

By way of example Fig. 3 shows how the number of reinforcing wires may be increased from two to four after elements of the production length L have produced.

The additional wires 4b running off the stock spools 19 provided with catches or toothed racks are anchored by their beginnings to a coupling member 22 extending transversely across the production line and also passing through the heating duct not shown. The ends of the coupling member 22 are connected to tensile elements 24, wires or wire cables, which in turn are connected to a winch 23 each. By driving the winches 23 and at the same time locking the rollers 19 the reinforcing wires 4b are subjected to the desired initial tension without thus affecting the initial tension on the two other wires 4a. The tensile elements 24 pass through the heating duct not shown, but are disposed outside of the elements positioned on the production line. At each advance step of the building elements the winches 23 and the stock spools 19 are rotated simultaneously in such a manner that the coupling member 22 moves to the right from the point dd in Fig. 3 and the tension on the wires 4b is continuously maintained. When the point d--d has reached the point c-c the initial tension force can be transferred to the drive 17 by means of the draw device 18.

Fig. 4 shows diagrammatically how the production of building elements having four reinforcing wires can be changed over to the production of elements having two wires only. For this purpose the ends of the wires 4b to be removed are anchored to a coupling member 22 connected by means of the tensile elements 25 to the winches 23 which can be retarded in accordance with the desired initial tension in the wires 4b when the drive 17 pulls the wires to the right in Fig. 4 by means of the draw device 18. When the coupling member 22 has moved from the point d-d to the point c-c said coupling member can be removed. The winches 2b may be identical with stock spools 19 provided with a lock.

The device shown in Fig. has two endless draft ropes 27 extending along the production line and passing over a drive pulley 29 and a reverse pulley 28 each of the latter being adapted as a tensioning pulley and being under the action of an hydraulic press 30. At least one strand of the draft rope 27 passes within the heating duct not shown, but outside of the building elements being produced, and is detachably connected to two coupling members 22a and 22b. By means of the front coupling member 22a the full initial tension force is transferred to the driving rollers 29, since the front ends of the reinforcing wires are anchored to the coupling member 22a. The two central reinforcing wires 4a run off from the stock spools 19 provided with locks whilst, the two outside reinforcing wires 4b are anchored with their rear ends to the coupling member 22b in the example shown since in this case there is to be a changeover from production with four wires that with two. wires. If production withfour wires were to be con;

front coupling. member 22a can be removed; With further progress of the production the two coupling members 22a and 220 must be exchanged in their role continuously.

If an endless production belt is used, it can be used on its return path not'only for returning the empty shuttering or the finished building elements, but it can also be used for the production of pre-stressed building elements.

It may be of advantage to sink the whole device to such an extent that the heating duct is disposed completely below the surface of the ground. In this manner a better heating insulation is obtained and in addition the whole area between the production table and the cutting off device can be used as storage space.

Instead of by customary heating the concrete of the building elements can be made to set in the heating duct by high frequency heating, by infra-red irradiation, by treatment with gases and vapours, or by continuous vibration.

What I claim and desire to secure by Letters Patent is:

1. An apparatus for continuous production of prestressed reinforced concrete elements, including supporting means, a plurality of molding means for said elements, reinforcing means passing through said molding means consecutively, supply means for said reinforcing means, means for advancing said molding means along said supporting means, means for supplying concrete to said molding means, and means for severing said reinforcing means between adjacent elements on said supporting means, said supply means for said reinforcing means including spool feeding means, intermittently actuated locking means for said spool feeding means, and weighed means suspended on said reinforcing means for maintaining a predetermined stress on said reinforcing means, said weighted means being positioned between said locking means and said molding means.

2. The apparatus according to claim 1, said means for advancing said molding means including a reciprocating draw device for advancing each of said molding means upon arrival of the latter at a predetermined location and further locking means for maintaining said predetermined stress when said reciprocating draw device is being returned to said predetermined location while disengaged from said molding means.

3. An apparatus according to claim 2, including coupling means to which said reinforcing means are connected, the relative positions of said reinforcing means being different on either side of said coupling means, said relative positions representing a compacted position wherein all of said reinforcing means are included in said element and a distant position wherein only part of said reinforcing means are included in said element, whereby the number of reinforcing means passing through each element may be varied.

4. An apparatus according to claim 3, including a winch for each of said reinforcing means to be displaced and coupled thereto, said winch being positioned on that side of said coupling member where said reinforcing means are in said distant position.

5. An apparatus according to claim 1, said supporting means including an endless belt, and said means for advancing said molding means including a plurality of actuation of said belt said molding means are advanced and saidpredetermined stress on said reinforcing means is maintainedby the coaction of said lugs, said weighted pplly 'nieans, andsaid' locking means. i

References Cited'in the file of this patent UNITED STATES PATENTS I v Trickey et all May 16, 1944 Earlier et a1 m Feb. 5, 1946 D'anhofl Sept; 25; 1951' Schroder Aug. 19; 1952 FOREIGN PATENTS Sweden Mar; 23; 1946 Italy Nov. 20, 1947' 

